Integrated antenna in an aerial vehicle

ABSTRACT

Disclosed is a cross loop antenna system for an aerial vehicle. In one embodiment, the cross loop antenna system includes a cross bar antenna and a ground plane. The cross bar antenna includes two thin coplanar perpendicular bars that intersect in the middle and are parallel to the ground plane. Each bar couples to the ground plane at each end, comprising an antenna loop. Thus, the cross loop antenna system comprises two intersecting single-fed loops. The antenna can operate at a wavelength that is approximately twice the length of the bars. In such an embodiment, the antenna system may be resonant. The distance between the bars and the ground plane may be relatively small, thus minimalizing the vertical profile of the antenna. The antenna may be operated as a dual-band antenna and may produce an omnidirectional radiation pattern. An aerial vehicle may include two such antennas.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/514,121, filed on Jul. 17, 2019, which is a continuation of U.S.patent application Ser. No. 15/268,455, filed on Sep. 16, 2016, now U.S.Pat. No. 10,396,443, which claims the benefit of U.S. Provisional PatentApplication No. 62/269,880, filed on Dec. 18, 2015, the entiredisclosures of which are hereby incorporated by reference.

TECHNICAL FIELD

The disclosure generally relates to the field of antennas and inparticular to an antenna for an aerial vehicle.

BACKGROUND

Remote controlled unmanned aerial vehicles, such as quadcopters, areknown. Aerial vehicles continue to grow in popularity for both theircommercial applications as well as recreational uses by hobbyists.

The ability of remote controlled aerial vehicles to quickly traversespace and to access places that a user cannot provides for many usefulapplications. However, a remote controlled aerial vehicle must, ingeneral, maintain communicative contact with a remote controller, heldby the user. A loss of connection between a remote controlled aerialvehicle and its remote controller can be catastrophic. Without usercontrol, a remote controlled aerial vehicle may crash or may otherwisebe lost. Thus, the utility of an aerial vehicle is constrained by theeffective communication range of the receivers and transmitters in theremote controller and aerial vehicle. Therefore, an aerial vehicle musthave antennas capable of reliably transmitting and receiving signals toand from its remote controller at a wide range of distances and atdifferent relative orientations.

One conventional antenna for an aerial vehicle is an external antenna,such as a whip antenna. Whip antenna are relatively simple to implementand provide an omnidirectional radiation pattern, but are generallyconsidered aesthetically displeasing. Furthermore, an external antennacan easily be damaged and may even collide with objects, such as treebranches, during flight, potentially leading to a crash. Thus, antennaswhich are internal to the aerial vehicle are advantageous. However, theinternal antennas conventionally used by aerial vehicles often take uptoo much space within the aerial vehicle and/or do not have a suitablyomnidirectional radiation pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed embodiments have advantages and features which will bemore readily apparent from the detailed description, the appendedclaims, and the accompanying figures (or drawings). A brief introductionof the figures (FIGS.) is below.

FIG. 1 is an example of a remote controlled aerial vehicle incommunication with a remote controller.

FIG. 2 illustrates an example of a remote controlled aerial vehicle.

FIGS. 3A-3C illustrate an example rear cross loop antenna system for anaerial vehicle.

FIG. 4 illustrates a cross bar antenna.

FIG. 5 illustrates rear and front cross loop antenna systems coupled toa wireless communication circuit, according to an embodiment.

FIGS. 6A-6C illustrate a radiation pattern of a cross loop antenna,according to an embodiment.

FIG. 7 illustrates rear and front single loop antennas coupled to awireless communication circuit, according to an embodiment.

FIG. 8 illustrates rear and front cross loop antennas, each with fourantenna loops, in accordance with an embodiment.

DETAILED DESCRIPTION

The figures and the following description relate to preferredembodiments by way of illustration only. It should be noted that fromthe following discussion, alternative embodiments of the structures andmethods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof what is claimed.

Reference will now be made in detail to several embodiments, examples ofwhich are illustrated in the accompanying figures. It is noted thatwherever practicable similar or like reference numbers may be used inthe figures and may indicate similar or like functionality. The figuresdepict embodiments of the disclosed system (or method) for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles described herein.

Configuration Overview

Disclosed, by way of example embodiments, is a cross loop antenna systemfor an unmanned aerial vehicle. The cross loop antenna system includes across bar antenna and a ground plane. The cross bar includes antennaportions (e.g., two thin coplanar intersecting bars) that intersect inthe middle and are parallel to the ground plane. The antenna portionsmay be perpendicular or substantially perpendicular (i.e., within 10° ofbeing perpendicular). Each antenna portion connects (or otherwisecouples) to the ground plane at each end, resulting in an antenna loop.Thus, the cross loop antenna system comprises two intersectingsingle-fed loops. The antenna can operate at a wavelength that isapproximately twice the length of the antenna portions of the cross barantenna. In such an embodiment, the antenna system may be resonant. Thedistance between the antenna portions and the ground plane may berelatively small, thus minimalizing the vertical profile of the antenna.The antenna may be operated as a dual-band antenna and may produce anomnidirectional radiation pattern. An aerial vehicle may include twosuch antennas.

Example Aerial Vehicle Configuration

FIG. 1 illustrates an example embodiment in which the aerial vehicle 110is a quadcopter (e.g., a helicopter with four rotors). The aerialvehicle 110 in this example includes a housing 130 for a payload (e.g.,electronics, storage media, and/or camera), four arms 135, four rotors140, and four propellers 145. Each arm 135 mechanically may couple witha rotor 140 to create a rotary assembly. When the rotary assembly isoperational, all the propellers 145 spin at appropriate speeds to allowthe aerial vehicle 110 to lift (take off), land, hover, move, and rotatein flight. Modulation of the power supplied to each of the rotors 140can control the acceleration and torque on the aerial vehicle 110.

A gimbal 175 may be coupled to the housing 130 of the aerial vehicle 110through a removable coupling mechanism that mates with a reciprocalmechanism on the aerial vehicle 110 having mechanical and communicativecapabilities. In some embodiments, the gimbal 175 can be attached orremoved from the aerial vehicle 110 without the use of tools. A camera115 may be mechanically coupled to the gimbal 175, so that the gimbal175 steadies and controls the orientation of the camera 115. It is notedthat in alternate embodiments, the camera 115 and the gimbal 175 can bean integrated configuration.

The aerial vehicle 110 may communicate with a remote controller 120 viaa wireless network 125. In one embodiment, the wireless network 125 is along range Wi-Fi system. It also can include or be another wirelesscommunication system, for example, one based on long term evolution(LTE), 3G, 4G, or 5G mobile communication standards. In someembodiments, the wireless network 125 includes a single channel and theaerial vehicle 110 and the remote controller 120 implement a half-duplexsystem. In an alternate embodiment, the wireless network 125 includestwo channels: a unidirectional RC channel used for communication ofcontrol information from the remote controller 120 to the aerial vehicle110 and a separate unidirectional channel used for a video downlink fromthe aerial vehicle 110 to the remote controller 120 (or to a videoreceiver where direct video connection may be desired). Alternatewireless network configurations may also be used.

The remote controller 120 in this example includes a first control panel150, a second control panel 155, an ignition button 160, a return button165, and a screen 170. The first control panel 150 can be used tocontrol “up-down” direction (e.g., lift and landing) of the aerialvehicle 110. The second control panel 155 can be used to control“forward-reverse” or can control the direction of the aerial vehicle110. In alternate embodiments, the control panels 150, 155 are mapped todifferent directions for the aerial vehicle 110. Each control panel 150,155 can be structurally configured as a joystick controller and/or touchpad controller. The ignition button 160 can be used to start the rotaryassembly (e.g., start the rotors 140). The return button 165 can be usedto override the controls of the remote controller 120 and transmitinstructions to the aerial vehicle 110 to autonomously return to apredefined location. The ignition button 260 and the return button 265can be mechanical and/or solid state press sensitive buttons.

In addition, each button may be illuminated with one or more lightemitting diodes (LED) to provide additional details. For example the LEDcan switch from one visual state to another to indicate with respect tothe ignition button 160 whether the aerial vehicle 110 is ready to fly(e.g., lit green) or not (e.g., lit red) or whether the aerial vehicle110 is now in an override mode on return path (e.g., lit yellow) or not(e.g., lit red). It also is noted that the remote controller 120 caninclude other dedicated hardware buttons and switches and those buttonsand switches may be solid state buttons and switches. For example, abutton or switch can be configured to allow for triggering a signal tothe aerial vehicle 110 to immediately execute a landing operation and/ora return to a designated location.

The remote controller 120 can also include hardware buttons or otheruser input devices that control the gimbal 175 or camera 115. The remotecontrol 120 can allow it's user to change the preferred orientation ofthe camera 115. In some embodiments, the preferred orientation of thecamera 115 can be set relative to the angle of the aerial vehicle 110.In another embodiment, the preferred orientation of the camera 115 canbe set relative to the ground. The remote controller 120 may alsotransmit commands to the aerial vehicle 110 which are routed to thecamera 115 through the gimbal 175 to take a picture, record a video,change a picture or video setting, and the like.

The remote controller 120 also includes a screen (or display) 170 whichprovides for visual display. The screen 170 can be a touch sensitivescreen. The screen 170 also can be, for example, a liquid crystaldisplay (LCD), an LED display, an organic LED (OLED) display, or aplasma screen. The screen 170 allow for display of information relatedto the remote controller 120, such as menus for configuring the remotecontroller 120 or remotely configuring the aerial vehicle 110. Thescreen 170 also can display images or video captured from the camera 115coupled with the aerial vehicle 110, wherein the images and video aretransmitted to the remote controller 120 via the wireless network 125.The video content displayed on the screen 170 can be a live feed of thevideo or a portion of the video captured by the camera 115. It is notedthat the video content can be displayed on the screen 170 within a shorttime (e.g., up to fractions of a second) of being captured by the camera115.

The video may be overlaid and/or augmented with other data from theaerial vehicle 110 such as the telemetric data from a telemetricsubsystem of the aerial vehicle 110. The telemetric subsystem includesnavigational components, such as a gyroscope, an accelerometer, acompass, a global positioning system (GPS) and/or a barometric sensor.In one example embodiment, the aerial vehicle 110 can incorporate thetelemetric data with video that is transmitted back to the remotecontroller 120 in real time. The received telemetric data is extractedfrom the video data stream and incorporate into predefine templates fordisplay with the video on the screen 170 of the remote controller 120.The telemetric data also may be transmitted separately from the videofrom the aerial vehicle 110 to the remote controller 120.Synchronization methods such as time and/or location information can beused to synchronize the telemetric data with the video at the remotecontroller 120. This example configuration allows a user of the remotecontroller 120 to see where the aerial vehicle 110 is flying along withcorresponding telemetric data associated with the aerial vehicle 110 atthat point in the flight. Further, if the user is not interested intelemetric data being displayed real-time, the data can still bereceived and later applied for playback with the templates applied tothe video.

The remote controller 120 shown in FIG. 1 is a dedicated remotecontroller, but in alternate embodiments the remote controller 120 maybe another computing device such as a laptop computer, smartphone, ortablet that is configured to wirelessly communicate with and control theaerial vehicle 110.

The remote controller 120 may contain one or more internal directionalantennas. For example, the remote controller 120 may include two ceramicpatch antennas. In some embodiments, the controller 120 uses bothantennas for transmission and reception. In alternate embodiments, oneantenna is used for reception and the other for transmission. The remotecontroller 120 may also include a Yagi-Uda antenna, a log-periodicantenna, a parabolic antenna, a short backfire antenna, a loop antenna,a helical antenna, a phased array of antennas, some combination thereof,or any other directional antenna.

FIG. 2 illustrates an example of an aerial vehicle 110. The aerialvehicle 110 may be coupled to a camera 115 via a gimbal 175. The camera115 may capture video and send the video to the aerial vehicle 110through a bus of the gimbal 175. The aerial vehicle 110 may wirelesslytransmit the video to the remote controller 120. The aerial vehicle 110may include one or more internal antennas in the housing 130 forwirelessly transmitting and receiving signals to and from the remotecontroller 120.

FIG. 2 also illustrates a 3-dimensional Cartesian coordinate system withx-y-z axes 200. The x-y-z axes 200 constitute an orthogonal right-handedcoordinate system. The x-y plane is the horizontal plane and the z-axisis in the upward vertical direction. The x-axis points in the directionof the heading of the aerial vehicle 110. Herein, the components of theaerial vehicle 110 are described relative to this x-y-z coordinatesystem. In FIG. 2, the aerial vehicle 110 is depicted in its standardorientation. The standard orientation is the orientation in which theaerial vehicle 110 in still air can hover without moving or rotating. Insome embodiments, the standard orientation of the aerial vehicle 110 isthe orientation in which the axial direction of the rotors 140 isvertical.

FIGS. 3A-3C illustrate an example cross loop antenna system for theaerial vehicle 110. The cross loop antenna system 300 depicted in FIGS.3A-3C is located inside of the housing 130 of the aerial vehicle 110,for example, in the rear at the bottom. It is noted that the rear crossloop antenna system 300 is depicted from underneath in FIGS. 3A-3C. Thisrear cross loop antenna system 300 includes a cross bar antenna 310, aground plane 330, and a support structure 340. The cross bar antenna 310connects to the ground plane 330 at four electrical contacts: threeground contacts 312 and an impedance-matching ground contact 314. Thesupport structure 340 connects to the cross bar antenna 310 and theground plane 330. The rear cross loop antenna system 300 is connected toa feed line 320. The feed line 320 connects to both the cross barantenna 310 and the ground plane 330. FIG. 3A is an isometric view ofthe rear cross loop antenna system 300, FIG. 3B is an exploded view ofthe rear cross loop antenna system 300, and FIG. 3C is a bottom planview of the rear cross loop antenna system 300.

The cross bar antenna 310 is an electrical conductor (e.g., metal). Thecross bar antenna 310 may include first and second antenna portions. InFIG. 3 the first and second antenna portions are thin coplanar barswhich intersect at their respective centers. The antenna portions may beparallel to the horizontal (x-y) plane and to the ground plane 330. Theantenna portions may be of substantially the same length (i.e., thesmaller of the two antenna portions may be 85% as long as the longer ofthe two antenna portions or longer). The antenna portions may beperpendicular or substantially perpendicular (i.e., within 10° of beingperpendicular). In some embodiments, the antenna portions are notperpendicular. For example, one antenna portion may be oriented 45°relative to the other.

Each end of the two antenna portions connects to the ground plane 330.Both ends of the first antenna portion connect to “legs” which extendupwards in the positive z-direction to connect to the ground plane 330.Each leg connects to the ground plane 330 at a ground contact 312. Asdepicted in FIG. 3A-3C, the ground contacts 312 may be “feet” thatextend in the horizontal plane, to provide a relatively large area ofelectrical contact between the ground plane 330 and the cross barantenna 310. The ground contacts 312 and the ground plane 330 may besoldered together. The second antenna portion of the cross bar antenna310 connects to the ground plane 330 at one end by a leg connected to aground contact 312. This leg and this ground contact 312 are the same asthose of the first antenna portions. The other end of the second antennaportion connects to the impedance-matching ground contact 314. In someembodiments, the shape of the leg of the impedance-matching groundcontact 314 is configured so that the impendence of the cross barantenna 310 matches the impendence of the feed line 320. In alternateembodiments, the impendence-matching ground contact 314 has a differentshape (e.g., curved, looping, or square). In some embodiments, theimpendence-matching ground contact 314 is replaced with an on-boardtuning circuit (e.g., capacitive and/or inductive elements).

Described differently, the cross bar antenna 310 includes four antennasegments. Each of the four antenna segments may respectively have afirst and second end, wherein each of the first ends connects to theground plane 330, and wherein the second ends mutually connect together.Three of the antenna segments may connect to the ground plane 330 atrespective first ends with respective ground contacts 312. The otherantenna segment may connect to the ground plane 330 at the first endwith an impedance-matching ground contact 314.

The ground plane 330 is a thin plate of electrically conductivematerial, e.g., cut sheet metal. The ground plane 330 is parallel to thetwo antenna portions of the cross bar antenna 310. The edges of theground plane 330 may adjoin the interior surface of the housing 130 ofthe aerial vehicle 110. In some embodiments, the ground plane 330 andthe cross bar antenna 310 are the same piece of metal or are joined bywelding. The rear cross loop antenna system 300 may include two loops.Each loop may include an antenna portion of the cross bar antenna 310,two ground contacts (either two ground contacts 312 or theimpedance-matching ground contact 314 and the ground contact 312opposite it), and the ground plane 330. The two loops are connected atthe center of the two antenna portions of the cross bar antenna 310 andshare the ground plane 330.

The feed line 320 is a transmission line, such as a coaxial cable. Thefeed line 320 carries a signal from the rear cross loop antenna system300 when the rear cross loop antenna system 300 is transmitting asignal, and carries a signal from the rear cross loop antenna system 300when the rear cross loop antenna system 300 is receiving a signal. Oneterminal of the feed line 320 (e.g., the outer tubular conducting shieldof the coaxial cable) may connect to the ground plane 330. The otherterminal of the feed line 320 (e.g., the inner conductor of the coaxialcable) may connect the cross bar antenna 310. This terminal of the feedline 320 may connect to the end of one of the antenna portions of thecross bar antenna 310 (i.e., the terminal may connect to one of theantenna segments of the cross bar antenna 310). The terminal of the feedline 320 may connect to the end of the antenna portion with theimpedance-matching ground contact 314. In some embodiments, a matchingcircuit is coupled between the feed line 320 and the cross bar antenna310 for impedance matching.

The support structure 340 may connect to the ground plane 330 and thecross bar antenna 310. The support structure 340 is between the groundplane 330 and the cross bar antenna 310. The support structure 340prevents the shape of the cross bar antenna 310 from bending, twisting,or otherwise deforming thus maintaining the relative spacing between thecross bar antenna 310 and the ground plane 330. In some embodiments, thecross bar antenna 310 is affixed to the support structure 340 withfasteners (e.g., screws or bolts), adhesive, or an alternate means ofridged joining. The support structure 340 may be transparent or nearlytransparent in the frequency band or bands in which the rear cross loopantenna system 300 operates. The support structure 340 may be anelectrical insulator. In some embodiments, the support structure 340 isa plastic structure. In alternate embodiments, the support structure 340is omitted. In such embodiments, the cross bar antenna 310 may berigidly attached to a chassis, a monocoque, or a semi-monocoque of theaerial vehicle 110.

In some embodiments the support structure 340 includes dielectricmaterial. For example, a layer of dielectric material may be adjacent tothe ground plane 330. By dielectrically loading the rear cross loopantenna system 300, the size of the antenna can be reduced. Thedielectric material may also be between the ground plane 330 and thecross bar antenna 310 but not part of the support structure 340.

FIG. 4 illustrates an example cross bar antenna 310 from an isomorphicview. FIG. 4 illustrates the length 410 of the antenna portions of thecross bar antenna 310, the width 430 of the bars, and the height 420 ofthe legs, in accordance with an embodiment. These lengths 410 andheights 420 are given in terms of a free space wavelength, denotedherein as λ. In some embodiments, the wavelength λ is in the radiofrequency (RF) range. The wavelength λ may be the RF wavelength at whichthe rear cross loop antenna system 300 operates. The rear cross loopantenna system 300 may be resonant at the wavelength λ.

For a given wavelength λ (e.g., λ=12.5 cm), if the length 410 of theantenna portions of the cross bar antenna 310 are about half awavelength (λ/2), the rear cross loop antenna system 300 is resonant atthis wavelength λ. The rear antenna system 300 may have a fundamentalresonant wavelength of λ. The rear cross loop antenna system 300 may beresonant at more than one frequency and exhibits higher order modes. Insome embodiments, the rear cross loop antenna system 300 transmits orreceives at multiple resonant frequencies. For example, the rear crossloop antenna system 300 may be resonant at 2.4 GHz with higher ordermodes of 3.8 GHz and 5.8 GHz. The rear cross loop antenna system 300 mayoperate as a dual-band antenna with operating frequencies of 2.4 GHz and5.8 GHz.

In the cross bar antenna 310 shown in FIG. 4, the height 420 of the legsis the displacement between the antenna portions of the cross barantenna 310 and the ground plane 330. In FIG. 4, this displacement is10% of the wavelength (λ/10). In general, a cross loop antenna system300 with a larger displacement between the ground plane 330 and theantenna portions of the cross bar antenna 310 has a better bandwidth andradiation efficiency. However, a cross loop antenna system 300 with alarger displacement will also have a larger profile and thus requiremore space within the aerial vehicle 110. A cross bar antenna 310 withlegs that are between 5% and 15% of the wavelength λ provides a usefulcompromise between the goals of minimalizing the antenna profile andproviding adequate performance. That is, in some embodiments, thedistance between the antenna portions of the cross bar antenna 310 andthe ground plane 330 is between 10% and 30% of the length 410 of theantenna portions. However, the displacement between the antenna portionsand the ground plane 330 may be less than λ/20 if a smaller profile isrequired or greater than 3×λ/20 if a better radiation efficiency orbandwidth is required.

The width 430 of the antenna portions of the cross bar antenna 310 maybe relatively small compared to the length 410 of the antenna portions.In FIG. 4, the width 430 of each antenna portion is one sixteenth of thewavelength (λ/16). In general, the width 430 of the antenna portion isbetween 3 and 12 mm. The antenna portions of the cross bar antenna 310may have a uniform thickness. The legs of the cross bar antenna 310 mayhave this same thickness. As illustrated in FIG. 4, the thickness ofeach antenna portion of the cross bar antenna 310 may be significantlyless than the width 430 of the antenna portion. The cross bar antenna310 may be, for example, between 0.5 and 2 mm thick. In someembodiments, the cross bar antenna 310 is manufactured by cutting andbending sheet metal.

In some embodiments, the total length of each antenna loop of the crossloop antenna system 300 is about a single wavelength λ. The total lengthof an antenna loop may be the sum of the length 410 of an antennaportion of (e.g., λ/2), the height 420 of two legs (e.g., both λ/10),and the length of the distance between the two ground contacts 312 ofthe loop (e.g., λ/2). In FIG. 4, the length of an antenna loop isλ/2+λ/10+λ/10+λ/2=1.2λ. The length of a loop of the cross loop antennasystem 300 may be, for example, between 1.1×λ and 1.3×λ.

In some embodiments, the rear crossed loop antenna system 300 includesan alternate antenna instead of the cross bar antenna 310. Like thecross bar antenna 310, this alternate antenna may include twoperpendicular or substantially perpendicular conductor elements joinedat their respective centers which run parallel to the ground plane 330and connect to the ground plane 330 at the end of each conductor elementto form two perpendicular or substantially perpendicular loops. Theconductor elements may be similar to the bars of the cross bar antenna310, but have different cross sections. For example, the conductorelements may be wires instead of bars.

FIG. 5 illustrates an example antenna system. The antenna system 505including a rear cross loop antenna system 300, a front cross loopantenna system 500, a wireless communication circuit 550, and two feedlines 320, 520. The front cross loop antenna system 500 and the rearcross loop antenna system 300 couple to the wireless communicationcircuit 550 via the feed line 520 and the feed line 320, respectively.Like the rear cross loop antenna system 300, the front cross loopantenna system 500 includes a cross bar antenna 510, a ground plane 530,and a support structure 540. The rear and front antenna systems 300, 500are placed sufficiently far apart to provide for adequate antenna toantenna isolation (e.g., low mutual coupling). For example, theseparation between the front cross loop antenna system 500 and the rearcross loop antenna system 300 may be 60 mm or greater.

In some embodiments, the aerial vehicle 110 includes a single cross loopantenna system which may be in the rear, the front, or the middle of theaerial vehicle 110.

The front cross loop antenna system 500 may be similar in structure andfunction to the rear cross loop antenna system 300. In FIG. 5, the crossbar antenna 510 and the support structure 540 of the front cross loopantenna system 500 are mirrored versions of the cross bar antenna 310and the support structure 340 of the rear cross loop antenna system 300.The ground plane 530 of the front cross loop antenna system 500 may be adifferent shape than the ground plane of the rear cross loop antennasystem 300. The two ground planes 330, 530 may be coplanar. In alternateembodiments, the cross bar antenna 510 of the front cross loop antennasystem 500 has a different length than that of the cross bar antenna 310of the rear cross loop antenna system 300. Accordingly, the resonantfrequencies of the two cross loop antenna systems 300, 500 may bedifferent. Additionally, the widths or the heights of the bars of thecross bar antennas 310, 510 or the heights of the bars of cross barantennas 310, 510 from their respective ground planes 330, 530 may bedifferent.

The wireless communication circuit 550 may be a transmitter, a receiver,or a transceiver. The wireless communication circuit 550 may transmitand/or receive data to communicate over the wireless network 125. Priorto transmitting data, the wireless communication circuit 550 may processthe data by performing encryption, forward error correction (FEC)coding, lossless compression, lossy compression, packetizing the data,or some combination thereof. The wireless communication circuit 550 maymultiplex data from multiple data streams of the aerial vehicle 110 orallocate data among a number of wireless channels. The wirelesscommunication circuit 550 may also encode a data stream for path orspatial diversity. Similarly, the wireless communication circuit 550 mayprocess data received over the wireless network 125 by performingdecryption, error correction decoding, decompression, or somecombination thereof. The wireless communication circuit 550 may alsodemultiplex data into multiple data streams.

FIGS. 6A-6C illustrate a radiation pattern of a cross loop antennasystem, according to an embodiment. Each figure is a plot of thefar-field radiation pattern of a cross loop antenna system (e.g., therear cross loop antenna system 300 or cross loop antenna system 500) ina different coordinate plane. The antenna is centered at the origin ofthe x-y-z coordinate system. FIGS. 6A, 6B, and 6C illustrate threecross-sections of the radiation pattern: a cross section 610 with thex-y plane, a cross section 620 with the x-z plane, and a cross section630 with the y-z plane. The radiation pattern is omnidirectional and hasnulls (i.e., a direction of no radiated energy) along the vertical axisin both directions. Herein, an omnidirectional radiation pattern refersto a radiation pattern that is approximately the same along thehorizontal plane (i.e., the x-y plane) as an ideal omnidirectionalradiation pattern. The radiation pattern is “donut shaped,” i.e.,similar in shape to a torus. In some embodiments, the cross loop antennamay be linearly polarized. In alternate embodiments, the antenna isdual-fed and is circularly polarized.

FIG. 7 illustrates an example antenna system with rear and frontsingle-loop antennas coupled to a wireless communication circuit,according to an embodiment. The antenna system 700 may include a rearsingle-loop antenna system 710, a front single-loop antenna system 720,a wireless communication circuit 550, and two feed lines 320, 520. Theantenna system 700 illustrated in FIG. 7 may be similar to the antennasystem 505 illustrated in FIG. 5, except that the front and rearsingle-loop antenna systems 720, 710 shown in FIG. 7 include respectivesingle-loop antennas 730 instead of the cross bar antennas 310, 510 ofthe front and rear cross loop antenna systems 300, 500 shown in FIG. 5.

The single-loop antenna 730 of the rear single-loop antenna system 710may include a first antenna portion (e.g., a thin bar) with a first endand a second end. A ground contact 312 connects the first end to aground plane 330 of the rear single-loop antenna system 710 and animpedance-matching ground contact 314 connects the second end of thefirst antenna portion to the ground plane 330. A feed line 320 connectedto the second end of the first antenna portion drives the single-loopantenna 730. The rear single-loop antenna system 710 may have a loopthat includes the ground plane 330 and the first antenna portion, theground contact 312, and the impedance-matching ground contact 314 of thesingle-loop antenna 730.

Similarly, the single-loop antenna 730 of the front single-loop antennasystem 720 may include a second antenna portion (e.g., a thin bar) witha first end and a second end. A ground contact 312 connects the firstend to a ground plane 330 of the front single-loop antenna system 720and an impedance-matching ground contact 314 connects the second end ofthe second antenna portion to the ground plane 330. A feed line 520connected to the second end of the second antenna portion drives thesingle-loop antenna 730. The rear single-loop antenna system 710 mayhave a loop that includes the ground plane 330 and the second antennaportion, the ground contact 312, and the impedance-matching groundcontact 314 of the single-loop antenna 730.

In some example embodiments, the single-loop antennas 730 of the frontand rear are substantially perpendicular (i.e., within 10° of beingperpendicular). That is, the axes of the single-loop antennas 730 may besubstantially perpendicular. In such an example embodiment, the combinedradiation patterns of the rear single-loop antenna system 710 and thefront single-loop antenna system 720 may be omnidirectional. Because thecombined radiation pattern may be omnidirectional, an aerial vehicle(e.g., aerial vehicle 110) that includes the antenna system 700 canmaintain communication with a device (e.g., remote controller 120)through at least one of the single-loop antenna systems 710, 720 at anyyaw orientation.

FIG. 8 illustrates an antenna system with rear and front cross loopantennas, each with four antenna loops, in accordance with anembodiment. The antenna system 800 may include a rear four-loop antennasystem 810, a front four-loop antenna system 820, a wirelesscommunication circuit 550, and two feed lines 320, 520. The antennasystem 800 illustrated in FIG. 8 may be similar to the antenna system505 illustrated in FIG. 5, except that the rear and front four-loopantenna systems 810, 820 shown in FIG. 8 include respective four-loopantennas 830.

Each of the four-loop antennas 830 includes four antenna portions (e.g.,thin bars parallel to the x-y plane) with respective first ends andsecond ends. For three of the four antenna portions, both the first andsecond end may connect to one of the ground planes 330, 530 at groundcontacts 312, 512. The other antenna portion may connect to the groundplane 330, 530 at a first end at a ground contact 312 and connects toone of the feed lines 320, 520 at the second end. The second end of thisantenna portion may also connect to the ground plane 330, 530 with animpedance-matching ground contact or an on-board tuning circuit. Theantenna portions may all be substantially the same length (i.e., theshortest of the antenna portions may be 85% as long the longest antennaportion or longer).

The loops of the four-loop antennas 830 may be evenly spaced. Forexample, in FIG. 8, the four loops of the rear four-loop antenna system810 are each separated by an angle of 45°. The rear and front four-loopantenna systems 810, 820 may each produce omnidirectional radiationpatterns. Although FIG. 8 illustrates antennas with four loops,alternate embodiments may include antennas with a different number ofloops.

Additional Considerations

The disclosed configuration describes a cross loop antenna system for anaerial vehicle. In one embodiment, the cross loop antenna systemincludes a cross bar antenna and a ground plane. The cross bar antennaincludes two thin coplanar bars that intersect in the middle and areparallel to the ground plane. The two bars may be perpendicular. Eachbar connects to the ground plane at each end, comprising an antennaloop. Thus, the cross loop antenna system comprises two intersectingloops, which are single-fed. The feed line connected to one of theantenna loops drives the other antenna loop. The antenna can operate ata wavelength λ that is approximately twice the length of the bars of thecross bar antenna. In such an embodiment, the antenna system may beresonant. The distance between the bars and the ground plane may berelatively small, thus minimalizing the vertical profile of the antenna.The antenna may be operated as a dual-band antenna and may produce anomnidirectional radiation pattern. An aerial vehicle may include twosuch antennas.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in example configurationsmay be implemented as a combined structure or component. Similarly,structures and functionality presented as a single component may beimplemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses of a machine (e.g., a computer) that manipulates or transformsdata represented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, may also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the invention. Thisdescription should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs for thedisclosed crossed loop antenna. Thus, while particular embodiments andapplications have been illustrated and described, it is to be understoodthat the disclosed embodiments are not limited to the preciseconstruction and components disclosed herein. Various modifications,changes and variations, which will be apparent to those skilled in theart, may be made in the arrangement, operation and details of the methodand apparatus disclosed herein without departing from the spirit andscope defined in the appended claims.

What is claimed is:
 1. An antenna system, comprising: a ground plane; afirst antenna loop coupled to the ground plane, the first antenna loopincluding a first antenna portion; and a second antenna loop coupled tothe ground plane, the second antenna loop including a second antennaportion, the second antenna portion intersecting with the first antennaportion, an edge of the ground plane directly adjoining an interiorsurface of an unmanned aerial vehicle.
 2. The antenna system of claim 1,wherein the first antenna portion is substantially perpendicular to thesecond antenna portion.
 3. The antenna system of claim 1, wherein thesecond antenna loop is coupled to the ground plane via a ground contactthat is an impedance-matching ground contact.
 4. The antenna system ofclaim 3, wherein the second antenna portion includes a first end and asecond end, further comprising: a feed line coupled to theimpedance-matching ground contact between the second end of the secondantenna portion and the ground plane.
 5. The antenna system of claim 4,wherein a shape of the impedance-matching ground contact is configuredto match an impedance of the antenna system with an impedance of thefeed line.
 6. The antenna system of claim 1, wherein both the firstantenna loop and the second antenna loop are closed loops.
 7. Theantenna system of claim 1, wherein the intersection of the first antennaportion and the second antenna portion is substantially centered on thefirst antenna portion and on the second antenna portion.
 8. The antennasystem of claim 1, further comprising: a support structure inside ofboth the first antenna loop and the second antenna loop.
 9. The antennasystem of claim 8, wherein the support structure is an electricalinsulator.
 10. The antenna system of claim 1, wherein a radiationpattern of the antenna system is omnidirectional.
 11. The antenna systemof claim 1, wherein a first length between a first end and a second endof the first antenna portion is substantially the same as a secondlength between a first end and a second end of the second antennaportion.
 12. The antenna system of claim 11, wherein the first length ishalf of a wavelength of an operating frequency of the antenna system,and wherein the antenna system is resonant at the wavelength of theoperating frequency.
 13. The antenna system of claim 1, wherein thefirst antenna portion has a first end and a second end, wherein thefirst antenna portion has a thickness, a width, and a length between thefirst end and the second end of the first antenna portion, the lengthbeing greater than the width and the width being greater than thethickness.
 14. The antenna system of claim 1, wherein a length of thefirst antenna loop is between 70% and 130% of a wavelength of anoperating frequency of the antenna system.
 15. The antenna system ofclaim 1, wherein the first antenna portion is coplanar with the secondantenna portion.
 16. The antenna system of claim 1, wherein both thefirst antenna portion and the second antenna portion are parallel to theground plane.
 17. The antenna system of claim 3, wherein the groundcontact of the second antenna loop are feet that extend along ahorizontal plane parallel to the ground plane.
 18. An antenna system ofan unmanned aerial vehicle, comprising: a ground plane; and a cross loopantenna coupled to the ground plane, the cross loop antenna including afirst antenna portion that intersects with a second antenna portion, anedge of the ground plane directly adjoining an interior surface of theunmanned aerial vehicle.
 19. The antenna system of claim 18, wherein theintersection of the first antenna portion and the second antenna portionis substantially centered on the first antenna portion and on the secondantenna portion.
 20. An unmanned aerial vehicle, comprising: an antennasystem, comprising: a ground plane, a first antenna loop coupled to theground plane, the first antenna loop including a first antenna portion,and a second antenna loop coupled to the ground plane, the secondantenna loop including a second antenna portion that intersects with thefirst antenna portion; and a wireless communication circuit coupled tothe antenna system via the first antenna loop and the second antennaloop, an edge of the ground plane directly adjoins an interior surfaceof a housing of the unmanned aerial vehicle.